1. Field
One embodiment of the invention relates to a pixel conversion device and a pixel conversion method, and the invention is effective to reduce color smears of characters, for example.
2. Description of the Related Art
In a terrestrial digital broadcast, a digital image signal including a digital luminance signal and a digital color-difference signal is transmitted in a format of 4:2:0. In recent years, the resolution of a digital television device has improved, so that opportunities to transmit a digital image signal including many characters through a digital broadcast have increased.
Therefore, in the digital television device, it has been desired to apply image-quality improving processing to the image signal including the characters. As regards a device for applying the image-quality improving processing, various techniques have been developed. For instance, patent document 1 (Jpn. Pat. Appln. KOKAI Publication No. 2004-304635) has disclosed a technique which creates a histogram of a luminance signal to set a background level for an object pixel. This technique applies prescribed image processing on the basis of the prescribed background level to improve contrast between the characters or the like and the background.
In patent document 1, as regards the luminance signal, the contrast between the characters and the background is good and the image quality of the image including the characters is improved. However, the digital image signal consisting of the luminance signal and the color-difference signal produces a problem that color smears occur at the peripheries of the characters. More specifically, if colored characters exist on a colored background, there is some possibility that the characters become vaguely-outlined.